From: Grant Grundler <grundler@parisc-linux.org>
To: Randolph Chung <randolph@tausq.org>
Cc: parisc-linux@lists.parisc-linux.org
Subject: Re: [parisc-linux] PATCH/RFC: discontig mem support for hppa
Date: Sat, 3 Jul 2004 12:37:12 -0600 [thread overview]
Message-ID: <20040703183712.GA10458@colo.lackof.org> (raw)
In-Reply-To: <20040703180852.GD18628@tausq.org>
On Sat, Jul 03, 2004 at 11:08:52AM -0700, Randolph Chung wrote:
> I am not clear about whether we need to treat "low memory"
> differently from "high memory" in any cases. willy pointed out to me
> that since we have a IOMMU we don't really need to care about ZONE_DMA
> vs ZONE_NORMAL,
That's correct. Becuase the virtual coherence index needed for cache
coherency, 32-bit PCI devices will always go through the IOMMU
even to DMA to physical memory < 4GB.
My hope is with ZX1 IOMMU, 64-bit devices can provide the virtual
coherence index as part of the DMA address. I haven't done all the
research yet to verify this will actually work.
grant
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next parent reply other threads:[~2004-07-03 18:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20040703180852.GD18628@tausq.org>
2004-07-03 18:37 ` Grant Grundler [this message]
2004-07-03 19:16 ` [parisc-linux] PATCH/RFC: discontig mem support for hppa Grant Grundler
[not found] ` <40E7028A.7060905@tiscali.be>
[not found] ` <20040703195349.GE18628@tausq.org>
[not found] ` <40E71BF2.2040601@tiscali.be>
[not found] ` <40E71D38.8010000@tiscali.be>
[not found] ` <40E71F91.2030001@tiscali.be>
2004-07-04 18:14 ` Randolph Chung
2004-07-05 12:46 Joel Soete
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